With all due respect and no need to be so dismissive and condescending: Just re-read my full essay which underlines that Spain's white rhino breeding program has not exactly taken off in earnest and not for want of stock nor new potential breeders. I think the net result over the last 2 decades has been a Mere 2 calves (2009, Madrid Zoo, M Cronos - passed away 2012 at Estepona - and 2013, Cabarceno, M Cosme). TBH: Births have been more accidental than a regular occurence. Within the Iberian Peninsula the exception being is actually Zoologico de Lisboa in Portugal who maintain a breeding group that produced regular offspring).Well, it's job of the EEP to change bulls, not of the parc. However, I don't think it's a good choice to start breeding with Martin in case that this is really wanted. He might genetically be the least interesting bull in Europe after having produced enough offspring in Hodenhagen plus being the son of two mass breeders. There are many more valuable bulls around who have already bred.
First and final, I have known full well this particular bull may be from an over-represented line. He was only recently substituted at Serengeti Hodenhagen by new bull Ekozu. His value is being a certified proven breeding bull and right now what the Iberian Peninsula and Spanish zoo collections exhibiting white rhinos really needs as part of the EAZA/EEP is calves on the ground.
FYI: The EAZA has actually been recommending and transferring in various females to 3-4 Spanish zoos as potential new breeding partners and no transfers will happen without prior consultation with nor recommendation from the studbook keeper.
Fact of the matter remains: ideally the bull/cow situation at Cabarceno, Tabernas (a Hodenhagen non-breeder, but it could also be the cow), Zoo Madrid (the current pair have been maintained since their younger years ...) and Terra Natura (old individuals and need for a bull to breed F Mayaji) all require close attention.